Croft



No. 6|7,889. Patented Ian. '17, 1899 J. l. THORNYGBOFT.

STEAM ENGINE.

(Application filed Dec. 19, 1894'.) (No Model.) 4 Sheets-Sheet l.

No. 6l7,889. Patented Jan. I7, I899,

J. I. THORNYCBOFT.

STEAM ENGINE. (Application filed Dec. 19, 1894.)

(No Model.) 4 Sheets-Sheet 2.

Q i I vVI LZMeaQx'eJ Ira/gm ms PETERS co. PHOTD-LITHO" wpnmsrcm u. c.

(No Model.)

Zk'ibnesses Patented Ian. I7, I899.

-J. l. THORNYCBUFT.

STEAM ENGINE.

(Application filed Dec. 19, 1894.)

4 Sheets-Sheet 3.

4752 t'eizzw THE NORRIS PETERS co. mom-mug WASHINGTON o, c.

No. .6l7,889. Patented Jan. l7, I899.

J. l. THORNYGRDFT.

STE-AM ENGINE.

(Application filed Dec; 19, 1894.) (No Model.) 4 Sheets-sheaf 4.

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PATENT JOllN ISAAC THORNYOROFT, OF LONDON, ENGLAND.

STEAM-ENGINE.

SPECIFICATI 0N forming part of Letters Patent No. 617,889, dated January 17, 1899.

Application filed December 19 1894. Serial No. 532,363. (No model.)

To ctZZ whom it may concern.-

Be it known that 1, JOHN IsAAo THORNY- CROFT, a subject of the Queen of Great Britain and Ireland, residing at Ohiswick, London, in the county of Middlesex, England, have invented Improvements in Steam-Engines, (for which I have obtained British Letters Patent dated July 11, 1893, No. 13,439,) of which the following is a specification.

. My invention has reference to an improved construction and arrangement of steam-engines for driving shafts, such as screw-propeller shafts.

It was long since proposed to reduce the friction of engines by using cranks opposite and adjacent with cylinders overlapping, but having their axes in a common plane. This arrangement involves an inconvenient height of engine andadds considerably to the weight. The use of cylinders inclined toward each other, with their axes in parallel planes and with pistons working onto oppositely-arranged and adjacent cranks, has alsobeen proposed; but in this arrangement the moving parts are not in all their positions effectually balanced.

Now with the view of securing the advantages of the known arrangement just above mentioned, while at the same time avoiding the increased height, I according to my invention construct an engine in which I make suiiicient angle between the cylinders to cause them to clear each other and place the cranks at an obtuse angle, differing from two right angles by the angle'between the cylinders.

I may provide four cylinders arranged in pairs. Their pistons work onto four cranks in a shaft carried by four bearings. The two cranks for each pair of cylinders are juxtaposed and connected by a common arm without any intervening bearing, and there are two bearings between the two pairs of cranks.

The two cranks forming each pair are arranged at such an angle that when one piston is at the end of its inward stroke the other will be at the end of its outward stroke, and a projection of the axis of either piston-rod will pass through the axes of its crank-pin and of the shaft. The caps of the crankshaft bearings are secured in position by extensions of the pillars that carry the engine cylinders. I

main bearings,due to the pressure on the piss tons, and also the vibration of the engine are very greatly reduced.

Triple-expansion and other engines may be constructed according to my invention.

In the accompanying drawings, Figure 1 is a side elevation, partly in section; Fig. 2, a plan; and Fig. 3, a cross-section on the line 0; cc of Fig. -1, showing so much of a four-cylinder triple-expansion double-acting engine as is necessary to illustrate the nature of my invention. Figs. 4, 5, 6, and 7 are detailviews drawn to a larger scale. Figs. 8 and 9 are central vertical sections in planes at right angles to each other, showing an automatic steam-valve, hereinafter referred to. Figs. 10 and 11 are detail views showing the relative position of the piston and cranks when the pistons are respectively at the bottom and top of their strokes.

Figs. 1, 2, and 3 are drawn to a smaller scale than the remaining figures.

The tripleex'pansion engine shown consists of two pairs of cylinders, the first pair 1 and 2 formin g the high and intermediate pressurecylinders, whilethe second pair 3 and 4, which are low-pressure cylinders, take the place of the one low-pressure cylinder found in ordinary triple-expansion engines. The cylinders of each pair are arranged at an angle a to each other, as seen in end view, with their axes in two vertical parallel planes transverse to the crank-shaft, so that the centers of the crank-pins can be brought closer together than would be possible if the cylinders were arranged in line with each other, the amount of such inclination being made as small as possible consistent with the attainment of this object. The pistons of the cylinders 1 and 2 work through connecting-rods in the usual way onto two cranks 6 6 and the pistons of the cylinders 3 and 4: work onto two similar cranks 6 6, the crank-shaft 7 being supported in four main bearings 8 8 8 8. The two cranks 6 6 are arranged on the shaft so that the angle between them on one side measures one hundred and eighty degrees minus the small or acute angle at which the two cylinders are inclined to each other and the angle between the cranks on the other side measures one hundred and eighty degrees plus the acute angle at which the two cylinders are inclined to each other. The angles between the two cranks are therefore both obtuse or wide angles, and the cranks are thus placed nearly opposite each other on the shaft end. When one piston is at the end of its upstroke, the other will be at the end of its downstroke, and the projection of each piston-rod will then pass through the axes of its crank-pin and of the crank-shaft. This construction and arrangement is clearly shown in Figs. 10 and 11. The cranks (3 6, connected to the pistons of the second pair of cylinders 3 and 4, are similarly arranged, the crank (5 being at right angles to crank 0 and crank 6 being at right angles to crank 6. By this construction the pressure of the pistons of each pair on the two crank-pins can be made to practically balance each other.

The engine will therefore be enabled to run at high speeds with little or no vibration, and the friction of the crank-shaft in its bearings is reduced and the strainon the shaft will be lessened when the load is placed on the engine. The two cranks forming each pair are connected by a common arm 0, so that there is no bearing between them, the bearings 8 and 8 being arranged between two pairs of cranks, as shown, and the others, 8 and 8, being at the respective ends of the crankshaft. Obviously instead of using two bearings 8 and 8 a single bearing of equivalent length may be used. Each arm 9 may advantageously be provided with a balanceweight 9, as shown in Fig. 4;. The said main bearings may, as shown, each consist of a separate casting, the several castings being connected on one side by a deep angle-bar 10 and on the other side by a fiat steel baseplate 10, as shown in Fig. 5. The cylinders of each pair are connected together and carried by two pairs of pillars 11, the pillars of each pair being brought so close together that they can be used as keep-bolts for the caps or keeps 12 of the main bearings, thereby reducing the weight of the engine. For this purpose the lower ends of the pillars are made to pass through the keeps and are screwed into the corresponding main hearing, and these ends are enlarged so that the nuts 13, which screw over them, can, when neeessary,be slipped up the plain parts of the pillars to enable the keeps to be raised. Each nut may be locked in place, when screwed down, by a set-screw 12. To enable the keeps to be easily removed from the pillars, each keep, while these are in position, may advantageously be formed at each end with a slot let and recess 15, as shown in Fig. 6, so that when the corresponding nuts 13 are screwed down the circular extensions 13 of such nuts will enter the recesses 15 and securely hold the keepin place, and when the nuts are raised the keep can be turned upward, so that the pillars will then pass through the slots 1a and enable the keep to be readily removed. This mode of utilizing the pillars that carry the cylinders as keep-bolts may advantageously be used in engines other than those the cylinders and cranks of which are arranged in the peculiar manner hereinabove explained.

To look the lower end of each pillar firmly in place and prevent it working loose, a cotter or wedge-shaped bolt 15*, Fig. 7, is arranged in an inclined hole 15 in the corre sponding main bearing in such a manner that it can be adjusted in an endwise direction and caused to bear against the bottom of the pillar, and thus prevent any play between the screw-threads on the pillar and those in the hole into which the pillar is screwed.

The pillars constituting each pair of pillars are in the example shown connected byastay 17, that forms a guide for the valve-rod, and the two pairs of pillars of each pair of cylinders are connected by a table or frame 18,that serves to stay the lower portions of the crosshead guides 19.

Suitable stays, such as 20 and 21, are provided to steady the engine. Some of these staysviz., 20go direct to the sides of the the vessel, while the othersviz., 2'1.-are attached to bosses 22, cast on prolongations of the castings forming the main bearings. These latter stays 21, together with the bedplate and pillars, form a series of triangles whereby a rigid structure is obtained.

7 In order to prevent the high-pressure piston exerting an unbalanced bending moment on the crank-shaft at starting, and thus to enable the said shaft to be made of lighter section than would otherwise be desirable, I consider it advantageous to place an automatic steam-valve 23, with pipe 23, between the main stop-valve 24, Figs. 1 and 2, and the steam-pipe 25, connecting the steamchest of the intermediate-pressure cylinder with the exhaust of the high-pressure cylinder 1, so that at starting live steam will be admitted simultaneously to both the high and intermediate pressure cylinders. By this means the intermediate-pressure piston will at starting be caused to exert a force tending to counteract the bending moment on the crank-shaf t produced by the high-pressure piston, and the steam thus admitted to the connectingpipe 25 will by creating a back pressure in the high-pressure cylinder further reduce the said bending moment.

Figs. 8 and 9 show a construction of automatic steam-valve that may conveniently be used for the purpose mentioned. It comprises a valve proper that consists of an annular flange 26 and hollow stem 26 and is arranged Within a case which is formed with a valve-seat 27 and steam inlet and outlet branches 28 and 28, respectively, whereof 28 is connected to the stop-valve 24: and 28 with the pipe 23. As will be seen, the valve is of differential type, so that if the area of the upper side of the valve exposed to steampressure and constituted by the flange 26, the upper annular end of the stem, and the lower central portion 26 of the stem, is n times the area of the lower side of the valve exposed to pressure, and which is constituted by the area of the lower side of the annular flange 26, the valve will close when the steam-pressure above the Valve is more than one-'nth of that below the Valve and will again open it the pressure falls below that limit. Thus with the arrangement described the valve will take steam from the engine side of the main stop-valve 24 and deliver it reduced to one-nth of its initial pressure to the connecting-pipe 25 and intermediate-pressure cylinder 2 for the purpose hereinbefore explained as soon as steam is admitted to the high-pressure cylinder 1, and when the engineisfairly at work the said valve will be automatically put out of action, provided that the pressure of the exhaust-steam from cylinder 1, which has access to pipe 25, be greater than one-nth that of the initial steam-pressure. The valve stem 26 is arranged to extend through a stutting-box 29, so that it can be moved by hand to ascertain that it is in working order. The

gland 30 may advantageously be recessed at 31 and be provided with a drain-pipe 32 to lead away any water or steam that may escape past the packingin the stuffing-box. A similar steam-valve may, if desired, be placed between the connecting-pipe 25 and the steamchests of the low-pressure cylinders 3 and 4, whereby the low-pressure pistons will be enabled to start the engine should the cranks connected to the high-pressure and intermediate-pressure pistons be on their dead-centers.

As will be obvious, an engine having a single pair of cylinders and cranks may be constructed according to my invention, and such an engine can be used for drivinga shaft other than a screw-propeller shaftas, for exam ple, the armature-shaft of a dynamo.

I am aware that it is old to arrange the cylinders of an engine at an acute angle to each other and also that it is old to arrange the cylinders of an engine at a right angle to each other and the cranks driven by the cylinders at the same angle, the arrangement of the cylinders and cranks being such that when the piston of one is at the end of the upstroke and the other is at the end of its downstroke the projection of the axis of each piston will pass through the axis of its crank-pin and that of the crank-shaft, and this construction I do not claim.

What I claim is 1. In a steam-engine, the combination with a pair of cylinders arranged at an acute angle to each other, of a crank-shaft, a pair of.

cranks thereon, the cranks being so arranged that the angle between them on one side measures one hundred and eighty degrees.

minus the acute angle between the cylinders and on the opposite side measures one hundred and eighty degrees plus the acute angle between the cylinders, the arrangement of cylinders and cranks being such that when the piston of one of the cylinders is at the end of its upstroke the piston of the other will be at the end of its downstroke, and the projection of the axis of each piston will pass through the axis of its crank-pin and that of the crank-shaft, substantially as described.

2. In a steam-engine, the combination with a pair of closely-adjacent overlapping cylinders arranged at an acute angle to each other, of a crank-shaft and a pair of cranks thereon, the cranks being so arranged that the angle between them on one side measures one hundred and eighty degrees minus the acute angle between the cylinders and on the opposite side measures one hundred and eighty de grees plus the acute angle between the cylinders, the arrangement of cylinders and cranks being such that when the piston of one of the cylinders is at the end of its upstroke the piston of the other will be at the end of its downstroke, and the projection of the axis of each piston will pass through the axis of its crankpin and that of the crank-shaft, substantially as described.

3. In a steam-engine, the combination with a pair of closely-adjacent overlapping cylinders arranged at an acute angle to each other, of a crank-shaft, a pair of cranks thereon, the cranks being connected by a common arm or web so that there is no bearing between.

them, and being so arranged that the angle between them on one side measures one hundred and eighty degrees minus the acute angle between the cylinders and on the opposite side one hundred and eighty degrees plus the acute angle between the cylinders the arrangement of cylinders and cranks being such that when the piston on'one of the'cylinders is at the end of its upstroke the piston of the other will be at the end of its downstroke, and the projection of the axis of each piston will pass through the axis of its crankpin and that of the crank-shaft, substantially as described.

4. In a compound engine having high and low pressure cylinders closely adjacent to and arranged at an acute angle to each other and having their axes in two parallel planes which are transverse to the axis of the crank-shaft, a crank-shaft, a pair of cranks thereon, the cranks being connected by a common arm or web so that there is no bearing between them, and being so arranged that the angle between them, on one side measures one hundred and eighty degrees minus the acute angle between the cylinders and on the opposite side one hundred and eighty degrees plus the acute angle between the cylinders, the arrangement of cylinders and cranks being such that when the piston on one of the cylinders is at the end of its upstroke, the piston of the other will be at the end of its downstroke, and the grees minus the acute angle between the cylinders and on the opposite side one hundred and eighty degrees plus the acute angle between the cylinders, thearrangement of cylinders and cranks being such that when the piston on one of the cylinders is at the end of its upstroke the piston of the other will be at the end of its downstroke, and the projection of the axis of each piston will pass through the axis of its crank-pin and that of the crankshaft, substantially as described.

6. In a triple-expansion engine comprising a pair of closely-adjacent high and intermediate pressure cylinders arranged at an acute angle to each other and overlapping, a pair of low-pressure cylinders similarly arranged, a common crank-shaft, two pairs of cranks on the shaft, the cranks of each pair being so arranged that the angle between them on one side measures one hundred and eighty degrees minus the acute angle between the cylinders and on the opposite side one hundred and eighty degrees plus the acute angle between the cylinders, the arrangement of the cylinders and cranks being such that when one piston of one pair of cylinders is at the end of its upstroke the other piston of that pair will be at the end of its downstroke, and the projection of the axis of each piston passes through the axis of its crank-pin and that of the crank-shaft, substantially as described.

7. In a steam-engine, the combination of an overhead cylinder having its piston working onto a crank-shaft below, a bearing for said crank-shaft, pillars arranged to support said cylinder above said bearing and to form keepbolts for the cap or keep of said bearing, and fastening devices carried by said pillars and serving to retain said cap or keep in place,

substantially as herein described.

8. In a steam-engine, the combination of an overhead cylinder having its piston working onto a crank-shaft below, a bearing for said crank-shaft, pillars arranged to support said cylinder and screwed into said bearings to serve as keep-bolts therefor, fastening devices carried by said pillars and serving to retain the cap or keep of the bearing in place, and wedging devices arranged to bear against the lower ends of said pillars and lock the same firmly in place, substantially as herein described.

9. A triple-expansion engine comprising the pair of rigidly-connected high and low pressure cylinders 1 and 2 with main stopvalve 24, the pipe 25 connecting the exhaust of cylinder 1 with the steam-chest of cylinder 2, an automatic steam-valve 23 with pipe 23* arranged between said stop-Valve and said steam-pipe,the pair of directly-connected low-pressure cylinders 3 and 4c, the cylinders in each pair being arranged overhead, inclined at a small angle to each other and so as to overlap one another, pillars supporting said cylinders, and a crank-shaft arranged below said cylinders and having two pairs of cranks, the crank-pins in each pair having their adjacent ends connected by a common web or arm arranged at an obtuse angle to each other differing from two right angles by the angle between the corresponding pair of cylinders and so connected to the pistons of these cylinders that when one piston of the pair is at the end of its inward stroke the other will be at the end of its outward stroke and extensions of the axes of the corresponding piston-rods will pass through the axis of the crank-shaft and of the corresponding crank-pins, and the respective cranks in one pair being at right angles to the respective cranks in the other pair, substantially as herein described and for the purpose specifled.

10. A triple-expansion engine comprising a high and an intermediate pressure cylinder rigidly and directly connected together, a pair of low-pressure cylinders connected rigidly and directly together, and two pairs of cranks on a common shaft, the cylinders in each connected pair being arranged close together at a small angle to each other sufficient to clear and overlap one another, and the cranks composing each pair being arranged at an obtuse angle to each other differing from two right angles by the angle between the corresponding pair of cylinders and having their adjacent ends carried solely by a common web or arm, said cranks being so arranged relatively to the piston of said pair of cylinders to which they are connected that when one piston is at the end of its inward stroke the other will be at the end of its outward stroke and extensions of the axes of the piston-rods will pass through the axis of the crank shaft and of the corresponding crank-pins, substantially as described.

11. A compound steam-engine comprising a connected pair of overhead and overlapping high and low pressure cylinders arranged close together and inclined to one another at a small acute angle, cross-head guides connected at their upper ends to said cylinders, a crank-shaft below said cylinders, a base-plate with bearings for said shaft, two pairs of pillars arranged to support said cylinders above said bearings and to form keep-bolts for the caps or keeps of said bearings, fastening devices carried by said pillars and serving to retain said caps or keeps IOC IIC

in place, stays, each connecting the two pilname to this specification in the presence of lars comprising a pair and adapted to form a two subscribing witnesses.

guide for a Valve-rod, and a table or frame y 4 connecting the two pairs of pillars and ar- JOHN ISAAC THORNYQROFT' ranged to stay the lower portions of said cross- Witnesses:

head guides, substantially as described. PERCY E. MATTOOKS,

In testimony whereof I have signed my EDMUND S. SNEWIN. 

